Portable electronic devices have been used to communicate with a main device. For example, a hand-held remote may be used to control a television or personal computer.
Other applications of battery-operated devices exist which communicate with remote devices which are capable of display.
Mobile devices, such as media players, may also so communicate.
Some devices, such as conventional remote controls, simply have no display on them. This makes it difficult or impossible to convey to a user that the battery level on the remote control is approaching a critical level.